The first ten amendments to the U.S. Constitution were ratified in 1791.
Known collectively as the Bill of Rights, these amendments were ratified on December 15, 1791. They protect liberties including freedom of speech and religion, the right to keep and bear arms, protections against unreasonable searches, due process, and rights of people accused of crimes.
James Madison introduced a group of proposed amendments in the First Congress in 1789. He drew on state declarations of rights and responded to concerns that the Constitution gave the federal government too much power without explicitly protecting individual liberties. Congress sent 12 amendments to the states, but only 10 were ratified at that time.
One proposed amendment concerning congressional apportionment did not become part of the Constitution then. Another concerning congressional pay was eventually ratified in 1992 as the Twenty-seventh Amendment. This is why the Bill of Rights contains 10 amendments even though Madison originally presented 12 proposals.
The Bill of Rights originally constrained the federal government; many of its protections were later applied to the states through the Fourteenth Amendment.